The way I see it (or atleast what I've read about) is that the VC emulators are pretty much the same apart from there are settings that are configured to work for each Rom. Untill these settings are "hacked" or Nintendo release a VC game with settings that work for all Roms (very unlikely) 100% compatibility will never happen. I hope that somebody more up-to-date corrects me on this issue but I think that is the case.